We've had 3 multicolor cards in the history of Core Sets. 20 seems too much. 10 would make sense, to show how Ravnica is about 2-color pairs. But is still a lot for a Core Set. (well, maybe we get a 3-color card for Bant)

-A section was added for multicolored cards due to the card seen on this picture: http://imgur.com/PCOzlUC, this does not however 100% confirms gold cards in the set.

Looks like Deflecting Palm to me.. But I'm probably wrong.

Some CSI guys enlarged it, and it doesn't look like anything we know. To me it looks like a knight with a cape genuflecting with his arm stretched forward. It's definitely a creature as it has a p/t box.

Didn't they say they wanted to add 20 gold cards to each large set to help draft? To give you an idea of a direction for your deck if you choose to draft that pair? That's why large sets went from 249 to 269

Look at vastwood gorger at 208 and veteran's sidearm at 242. There can't be 32 artefacts. This doesn't follow the rules of standard core sets, they are introducing new mechanics.

Didn't they say they wanted to add 20 gold cards to each large set to help draft? To give you an idea of a direction for your deck if you choose to draft that pair? That's why large sets went from 249 to 269

I understand that they increased the number of different uncommons by 20 to go from 249 to 269 in M15, but I don't know of a statement specific to gold cards. Specifically for M15 there wasn't a cycle of gold cards, if I remember correctly, though that doesn't mean there isn't one here.

Updated the list to add Displacement Wave (with unconfirmed name for now)

I wanted to add rarities for the sample decks cards, but it seems like there will be a few rarity bumps, and I'm not sure where they'll go. Each sample deck in M15 had 4 uncommons, and it seems to be the same for the white, blue and green ones in Magic Origins, however black is missing one and red is missing two.

I think Cruel Revival is very likely to get bumped to uncommon, but the cards in the red deck are pretty bad and I have no idea which could be bumped up in rarity. My guess would be Runed Servitor (because they love putting bad artifact creatures at uncommon) and maybe Fiery Conclusion (because it lets red kill a bomb)...